In an optical disk apparatus for reading and reproducing a signal recorded in a recording track on an optical disk, a pickup head is moved to a target track so that an optical beam may be projected thereon in order to read a recorded signal.
Before the optical pickup head is moved, an initialize operation is performed to position the optical pickup at a known track on the optical disk. FIG. 3 is a schematic view showing the construction of a conventional optical disk drive apparatus. In the figure, a linear scale 1 having notched grooves is attached to a drive apparatus body (not shown in the figure) and a dedicated sensor 2 for reading the number of the grooves on the linear scale 1 is attached to an optical pickup 3.
In an initializing operation in such a case, the optical pickup 3 is first driven to hold the optical pickup 3 against one end of the linear scale 1. Then the optical pickup 3 is moved from that end toward the other end. Sensor 2 reads the number of grooves through which the optical pickup 3 is moving. When the number of grooves (tracks) read by the dedicated sensor 2 reaches a predetermined number, the optical pickup 3 stops. Thus the optical pickup 3 apparatus can be positioned near the mid-range of the optical disk.
Further, the optical pickup 3 can be moved to a target track under dedicated servo control through the use of the dedicated sensor 2.
Instead of the linear scale 1 and the dedicated sensor 2, means such as a potentiometer, can be used.
In the conventional method for initializing an optical disk drive apparatus, a dedicated sensor for detecting the absolute position of an optical pickup is needed to position the optical pickup near the mid-range of the optical disk. This presents a problem in that an expensive large-sized apparatus is needed. In the case of a conventional optical disk drive apparatus which is not provided with the above dedicated sensor, there is another problem in that an initializing operation cannot be performed.